This invention is directed generally to telephone line test apparatus and more particularly to a phone line tester for interfitting with a modular telephone jack for testing the tip-ring polarity of the modular telephone jack.
Briefly, modular telephone equipment currently in use utilizes a wall-mounted receptacle comprising a modular telephone "jack" or socket capable of accepting a complementary modular telephone plug. This plug can be readily disconnected and connected to another similar modular jack or receptacle in another location. Certain telephone equipment further requires that the termina1s or contacts of each receptacle or modular maintain a predetermined tip-ring, that is, positive-to-negative polarity with respect to the central office equipment. It is, however, possible that such receptacles may inadvertently be miswired and that the final tip-ring polarity of the contacts could be wired in reverse polarity. Moreover, it is possible that one of the tip or ring lines leading to the contacts may be inadvertently broken, disconnected or improperly connected to a terminal or contact other than the proper tip or ring terminal or contact.
According1y, it is a general object of the invention to provide a telephone line tester for quickly and easily testing for the proper tip ring polarity of such a modular telephone jack or wall-mounted receptacle.
Broadly speaking, the concept of testing the tip-ring polarity of telephone receptacles or modular jacks is known, as shown for example in U.S. Pat. No. 4,209,671 Charles et al. and U.S. Pat. No. 4,373,120 to McDonald. The devices of both of these patents utilize as an indicator a lamp or other light-emitting element of a type which requires that a further polarity sensitive element, such as a diode, be additionally coupled across the tip-ring lines during testing. This is required in order to complete the circuit and/or to assure that only the proper polarity of the tip-ring voltage will cause the indicator lamp or other element to light.
Moreover, the device of the Charles, et al. patent further includes a battery for testing the modular jack even in the absence of a connection thereof to the central office. Hence, this battery replaces the tip-ring voltage normally provided from the central office or other outside equipment. Accordingly, the device of Charles, et al. can test only the continuity or proper connection of the tip-ring lines, and not the presence and proper polarity of the tip-ring voltage from the central office. This device further requires that the additional polarity-sensitive element or diode be coupled to the line at some point removed from the modular jack or receptacle being tested. For example, the diode is to be connected near a station protector located near the entrance of the phone line to the subscriber's location or even back at the central office.
The McDonald patent additionally requires that a resistor element of a predetermined value be coupled in circuit with the diode and neon tube indicator so as to provide a characteristic "signature" or signal. This signal is recognizable by the telephone central office equipment for purposes of making a continuity test on a subscriber line from the central office. Hence, the McDonald patent does not necessarily contemplate on-site testing of the equipment or of the modular jack.